O.C.'ing
I agree with ZBLOWFISH, if there was no chance (or a VERY low) chance that something would be damaged, then I would consider OC'ing. It would be wasting my money (and my time) if I had to fix my computer after OC'ing caused damage.
Its a marginal cost/benefit issue. Will the benefit of OC'ing outweigh the damage it may cause? In my case the benefit will almost never outweigh the costs, so I dont do it.
Though its pretty cool when someone can do it and make it work well. I've seen some really cool OC'ed computers. OverClockers are the Richard Pettys of the computer world, they can do what most people wont, or cant do.